Filter for compressed air

ABSTRACT

A filter device including a first filter having a first packing accommodated in a first sleeve thereof, and a second filter having a second packing accommodated in a second sleeve thereof, each one of the first and second packings cooperating with two retainer plates and a core bar to constitute a corresponding one of first and second filter elements, the two retainer plates being disposed on axially opposite ends of the corresponding one of the first and second packings, the core bar axially extending to pass through a center of the corresponding one of the first and second packings such that the two retainer plates engage the core bar at respective opposite ends of the core bar, the core bar being provided with a pull tab at one of the opposite ends of the core bar, so that the first and second packings are introduced and removed into and from the first and second sleeves, respectively.

TECHNICAL FIELD

The present invention relates in general to a filter device forcompressed air which has filter means having suitable packingsaccommodated in sleeves.

BACKGROUND ART

Generally, passages for supplying compressed air to variouspneumatically operated components used in various factories and atomicplants, for example, are usually provided with filter devices forremoving water and oil contained in the compressed air, for the purposeof protecting the pneumatic components or improving the performance ofthose components.

One type of such a filter device for compressed air is disclosed inJP-A-5-200217, which is constructed to include two kinds of filtermeans. Namely, this filter device has first filter means having asuitable first packing accommodated in a sleeve, and second filter meanshaving a suitable second packing accommodated in another sleeve. Thefirst and second filter means are disposed parallel to each other. Atone of axially opposite ends of the first and second filter means, thereis disposed a manifold which includes an inlet passage portion and anoutlet passage portion. The inlet passage portion has an inlet passageformed therein, through which the compressed air is introduced into thefilter device. The outlet passage portion has an outlet passage formedtherein, through which the compressed air is fed out from the filterdevice. The inlet and outlet passages communicate with the first andsecond filter means, respectively. At the other of axially opposite endsof the first and second filter means, there is disposed an enclosed trapchamber having a suitable volume, such that each of the first and secondfilter means communicates with the trap chamber. The thus arranged firstand second filter means, the trap chamber and the manifold are assembledtogether and fixed to each other by a plurality of bolts which extendthrough the manifold and which are screwed in the trap chamber.According to this arrangement, the compressed air entering the inletpassage of the manifold is fed into the outlet passage of the manifoldthrough the first filter means, the trap chamber, and the second filtermeans, whereby an air passage for the compressed air is formed throughthe filter device.

In the filter device constructed as described above, usually, the firstpacking of the first filter means is a roll of a wire mesh fabric formedby weaving or knitting stainless steel fibers or other metallicmaterials, so that vapor and/or liquid particles like water and oilcontained in the compressed air are condensed or coalesced as thecompressed air passes through the first filter means, while the secondpacking of the second filter means is a wound fabric mesh formed byweaving or knitting cotton fibers or other materials, so that the liquidparticles contained in the compressed air are absorbed or vaporized asthe compressed air passes through the second filter means.

Thus, in the filter device disclosed in the above-indicated publication,the vapor and/or liquid particles are condensed or coalesced as thecompressed air is introduced into the trap chamber through the inletpassage of the manifold and the first filter means, so that the vaporand/or liquid particles are separated from the compressed air. Further,the compressed air from which the vapor and/or liquid particles havebeen thus separated is introduced into the second filter means throughthe trap chamber, so that the amount of the liquid particles remainingin the compressed air is minimized.

The first and second packings constituting the first and second filtermeans, respectively, are required to be replaced with clean ones whenthe packings get clogged with dust and/or grease. The replacementrequires the following operations.

First, the plurality of bolts serving to connect the first and secondfilter means, the manifold and the trap chamber into an integralassembly are all removed, and the assembly is disassembled into the fourparts. Secondly, the clogged first and second packings which areaccommodated in the first and second sleeves, respectively, are replacedwith clean ones. The first and second filter means, the trap chamber andthe manifold are then reassembled together and fixed to each other, asdescribed before, by screwing the plurality of bolts in the respectivepositions.

That is, in the conventional filter device disclosed in theabove-identified publication, each time the first and second packings ofthe first and second filter means are replaced, the device has to bedisassembled into the parts before the replacement, and the parts haveto be reassembled into the device after the replacement.

The filter device is advantageously used in various factories, atomicplants and medical field owing to its high filtering performance.However, the filter device requires the above-described operations forreplacing the first and second packings, which operations are cumbersomeand time-consuming, as described above. There is still a room forimprovement in this filter device.

The present inventor disclosed a filter device for compressed air inJP-A-9-10533 having a construction which solves the problem with theabove-described filter device. The disclosed filter device includesfirst filter means having a first packing accommodated in a firstsleeve, second filter means having a second packing accommodated in asecond sleeve, an inlet passage portion defining an inlet passage whichconnects an exterior of the filter device and the first sleeve tointroduce the compressed air from the exterior into the first filtermeans, a guide passage portion defining a guide passage which connectsthe first sleeve and the second sleeve to guide the compressed air fromthe first filter means into the second filter means, and an outletpassage portion defining an outlet passage which connects the secondsleeve and the exterior to feed the compressed air out of the secondfilter means to the exterior. The first and second sleeves, the inletpassage portion, the guide passage portion and the outlet passageportion are formed of a synthetic resin, integrally with each other, soas to constitute a body of the filter device. The body is provided withaccess openings through which the first and second packings are removedfrom the filter device. To each of the access openings, a closure memberis removably attached so as to fluid-tightly close the access openings.

This filter device for compressed air is constructed such that all theparts cooperating to form a fluid passage in the filter device areformed of a synthetic resin, integrally with each other so as toconstitute the body of the filter device, and the body is provided withthe access openings through which the first and second packings areremoved. Further, the closure member is removably attached to each ofthe access openings so as to fluid-tightly close the access openings.According to this filter device, therefore, for replacing the cloggedfirst and second packings, it is not necessary to carry outtime-consuming operations such as disassembling of the filter deviceinto the component parts and reassembling of the parts into the device.In this filter device, the clogged first and second packings can bereplaced by new ones, by simply removing the caps from the respectiveaccess openings and re-attaching the caps to the respective accessopenings. Thus, the replacement of the first and second packings can bemade more easily and quickly than in the conventional device.

However, as a result of further study made by the present inventor, thisfilter device proved to have the following problem. Upon the replacementof the clogged first and second packings in this filter device, theclogged packings are removed by a suitable tool formed of a wire orother material, since it is very difficult for the operator to pick thepackings out of the respective sleeves, directly with the fingers. Thatis, the tool is put into the first and second sleeves through therespective access openings after removing the closure members from theaccess openings, so as to take out the clogged first and secondpackings. Thus, this filter device requires the tool for the replacementof the first and second packings and a certain amount of cumbersome workfor taking out the clogged first and second packings through the accessopenings from which the closure members have been removed, although thedevice is constructed such that the closure members can be removed fromthe access openings without using a tool.

DISCLOSURE OF INVENTION

The present invention was developed in the light of the abovesituations. It is therefore an object of the present invention toprovide an improved construction of the filter device for compressedair, which construction makes it possible to introduce and remove thepackings of the filter means without using any tools, for thereby easilyand quickly replacing the packings.

The above object may be achieved according to the present inventionwhich provides a filter device for compressed air including first filtermeans having a first packing accommodated in a first sleeve thereof,second filter means having a second packing accommodated in a secondsleeve thereof, an inlet passage portion defining an inlet passage whichconnects an exterior of the filter device and the first sleeve tointroduce the compressed air from the exterior into the first filtermeans, a guide passage portion defining a guide passage which connectsthe first sleeve and the second sleeve to guide the compressed air fromthe first filter means into the second filter means, and an outletpassage portion defining an outlet passage which connects the secondsleeve and the exterior to feed the compressed air out of the secondfilter means to the exterior, the compressed air which has beenintroduced through the inlet passage portion being introduced throughthe first filter means into the guide passage portion, whereby vapor orliquid particles contained in the compressed air are condensed orcoalesced to be separated from the compressed air, the compressed airfrom which the vapor or liquid particles have been separated beingfurther introduced through the guide passage portion into the secondfilter means, whereby the liquid particles remaining in the compressedair are removed, the filter device being characterized in that (a) thefirst and second sleeves, the inlet passage portion, the guide passageportion and the outlet passage portion are formed of a synthetic resin,integrally with each other, so as to constitute a body of the filterdevice, the body being provided with access openings through which thefirst and second packings are removed from the filter device, each ofthe access openings being provided with a closure member which isremovably attached to each of the access openings so as to fluid-tightlyclose the access openings, (b) the first sleeve includes a communicationportion which communicates with the inlet passage portion and which islarge enough to permit the first packing accommodated in the firstsleeve to be removed therethrough, while the second sleeve includes acommunication portion which communicates with the outlet passage portionand which is large enough to permit the second packing accommodated inthe second sleeve to be removed therethrough, the access openings beingformed in the inlet and outlet passage portions so that the first andsecond packings can be removed through the access openings from thefirst and second sleeves, respectively, and (c) each one of the firstand second packings cooperates with two retainer plates and a core barto constitute a corresponding one of first and second filter elements,the two retainer plates each having a plurality of through-holes formedtherethrough being disposed on axially opposite ends of thecorresponding one of the first and second packings, the core barextending in an axial direction of the corresponding one of the firstand second packings to pass a center of the one of the first and secondpackings such that the two retainer plates engage the core bar atrespective opposite ends of the core bar, the core bar being providedwith a pull tab at one of the opposite ends of the core bar, so that thefirst and second packings are introduced into and removed from the firstand second sleeves, respectively.

The above-described filter device for compressed air according to thepresent invention is constructed such that all the parts cooperating toform a fluid passage in the filter device are formed of a syntheticresin, integrally with each other so as to constitute a body of thefilter device, and the body is provided with access openings throughwhich the first and second packings are removed. Further, the closuremember is removably attached to each of the access openings so as tofluid-tightly close the access openings. According to the present filterdevice, therefore, for replacing the clogged first and second packings,it is not necessary to carry out time-consuming operations such asdisassembling of the filter device into the component parts andreassembling of the parts into the device. In this filter device, theaccess openings can be easily opened and closed, by simply removing thecaps from the respective access openings and reattaching the caps to therespective access openings. Thus, the first and second packings can beeasily made exposed.

Each one of the first and second packings cooperates with the tworetainer plates and the core bar to constitute a corresponding one ofthe first and second filter elements. The two retainer plates eachhaving the plurality of through-holes formed therethrough are disposedon the axially opposite ends of the corresponding one of the first andsecond packings, while the core bar extends in the axial direction ofthe corresponding one of the first and second packings to pass thecenter of the corresponding one of the first and second packings suchthat the two retainer plates are engaged with the core bar at therespective opposite ends of the core bar. The core bar is provided withthe pull tab at one of the opposite ends of the core bar, so that thefirst and second packings are introduced into and removed from the firstand second sleeves, respectively. This arrangement makes it possible toremove the clogged first and second packings together with the othercomponents of the above-described elements, out of the body of thefilter device through the access openings which have been opened byremoving the closure members, by simply pulling the core bar which is apart of the filter element, with the operator's finger engaging the pulltab. Besides, this arrangement makes it possible to accommodate newfirst and second packings together the above-described other components,in the body of the filter device, by simply pushing the core bar at thepull tab into the body of the filter device. Thus, the first and secondpackings can be removed from and introduced into the above-describedbody while the access openings are open, without a necessity of using atool. Thus, the replacement of the first and second packings can be mademore easily and quickly than in the conventional device.

Further, in the above-described filter device for compressed airaccording to the present invention, the core bars constituting the firstand second filter elements can be formed of a material such as asynthetic resin, together with the retainer plates, using a single mold.Thus, the present filter device can be produced without a considerableincrease in the production cost.

Further, since the filter device for compressed air is constructed suchthat all the parts cooperating to form the fluid passage in the filterdevice are formed of a synthetic resin, integrally with each other so asto constitute the body of the filter device as a single unit, asdescribed above, the present filter device assures a remarkable increasein its fluid-tightness reliability, as compared with that of theconventional device wherein separate parts are connected by boltsthrough suitable packings.

Still further, in the above-described filter device for compressed airaccording to the present invention, the inlet passage portion and theoutlet passage portion are provided with the respective access openings.Therefore, even if the compressed air leaks out from the body throughthe access openings, the air leakage has a comparatively small influenceon the flow velocity and the pressure of the compressed air flowingthrough the first and second sleeves and the guide passage portion, ascompared with an arrangement wherein the compressed air may leak throughthe first sleeve and/or the second sleeve and/or the guide passageportion. Accordingly, the present construction prevents or minimizesdeterioration of the filtering performance of the first and secondfilter means.

According to a first preferred form of the filter device for compressedair of the present invention, the first packing of the first filtermeans is a metallic fiber aggregation which is formed by aggregating alarge number of short or long fibers made of a metallic material, andwherein the first filter element is formed by fixedly winding theaggregation on the core bar. Thus, it is not necessary to weave or knitthe metallic fibers as required in the conventional device, forpreparing the first packing. The operation for the preparation of thefirst packing or the whole filter device is made easier, and thereforethe manufacturing cost is reduced. Besides, the first packing isconstituted by a comparatively small amount of the metallic fibers, butthe condensation and/or coalescence of the vapor and/or liquid particlesin the first filter means can be effected as efficiently as in theconventional device. Thus, the construction according to the presentfirst preferred form permits significant reduction of the weight of thefilter device and the material cost, without deteriorating the filteringperformance.

According to a second preferred form of the filter device for compressedair of the present invention, the second packing of the second filtermeans is a belt-like fabric mesh formed of cotton fibers, and whereinthe second filter element is formed by fixedly winding the belt-likefabric mesh on the core bar.

According to a third preferred form of the filter device for compressedair of the present invention, the body of the filter device is formed ofa transparent synthetic resin, as a single unit. This construction makesit possible to observe, through the transparent body, the state ofclogging of the first and second packings accommodated in the first andsecond sleeves and constituting the first and second filter means,respectively, and makes it easy to know a time of replacement of thefirst and second packings.

According to a fourth preferred form of the filter device for compressedair of the present invention, the closure member has at least one legprovided at a portion thereof opposed to the retainer plates andextending towards the retainer plates, and the closure member isattached to each of the access openings such that the retainer platesare pressed by the at least one leg of the closure member, whereby theretainer plates are prevented from moving upwardly. Thus, in the presentpreferred form, the engagement of the core bars of the first and secondfilter elements with the retainer plates effectively prevents upwardmovements of the retainer plates remote from the closure members, whichmay take place due to flow of the compressed air, or effectivelyprevents upward movements of the first and second packings, without theprovision of a complicated device. The pressure given by the leg of theclosure member to the retainer plates is released by removing theclosure member from the body. Therefore, the thus constructed structurefor preventing the upward movements of the packings does not bother thereplacement of the first and second filter elements, and does notdeteriorate the operation for replacing the first and second packings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an elevational view in vertical cross section showing oneexample of a filter device for compressed air having a constructionaccording to the present invention.

FIG. 2 is a plan view of the filter device shown in FIG. 1.

FIG. 3 is an elevational view in vertical cross section showing a bodyof the filter device of FIG. 1.

FIG. 4 is a view taken in a direction of arrow A in FIG. 3.

FIG. 5 is a view taken in a direction of arrow B in FIG. 3.

FIG. 6 is a cross-sectional view taken along line C--C in FIG. 3.

FIG. 7 is a view taken in a direction of arrow D in FIG. 3.

FIG. 8 is an elevational view in vertical cross section showing anexample of a closure member which is attached to the filter device shownin FIG. 1.

FIG. 9 is a view taken in a direction of arrow E in FIG. 8.

FIG. 10 is a view taken in a direction of arrow F in FIG. 8.

FIG. 11 is an elevational view in vertical cross section showing anexample of a drain unit which is attached to the filter device shown inFIG. 1.

FIG. 12 is a view taken in a direction of arrow G in FIG. 11.

FIG. 13 is an elevational view in vertical cross section showing anexample of a first filter element which is accommodated in the filterdevice shown in FIG. 1.

FIG. 14 is a view taken in a direction of arrow H in FIG. 13.

FIG. 15 is an illustration showing a first half of a process forfabricating the first filter element shown in FIG. 13.

FIG. 16 is an illustration showing a second half of the process forfabricating the first filter element shown in FIG. 13.

FIG. 17 is an illustration showing a first half of a process forfabricating one example of a second filter element which is accommodatedin the filter device shown in FIG. 1.

FIG. 18 is an illustration showing a second half of the process forfabricating one example of the second filter element which isaccommodated in the filter device shown in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

To further clarify the present invention, there will be described indetail one typical embodiment of the present invention by reference tothe drawings.

Referring first to FIGS. 1 and 2, there is schematically shown oneexample of a filter device for compressed air constructed according tothe present invention. As is apparent from the figures, the filterdevice 10 consists of a body 16, two caps 18, 18, a drain unit 20, afirst filter element 88 and a second filter element 90. The body 16accommodates the first and second filter elements 88, 90 therein. Thetwo caps 18, 18 are attached to a top of the body 16, and serve asclosure members. The drain unit 20 is attached to a bottom of the body16.

More specifically described, as shown in FIGS. 3 through 7, the body 16includes an inlet passage portion 22, an outlet passage portion 24, afirst sleeve 26 and a second sleeve 28 and a guide passage portion 30which are formed integrally with each other, and which cooperate toconstitute the body 16.

The inlet passage portion 22 consists of an inlet communication portion34 and an inlet portion 36. The inlet communication portion 34 takes asubstantially cylindrical shape having a large cylindrical wallthickness, and extends parallel to an axial direction of the body 16,i.e., extends in a vertical direction as viewed in FIG. 3. The inletcommunication portion 34 has an upper opening communicating with theexterior, and a lower opening communicating with the first sleeve 26.The inlet portion 36 takes a substantially cylindrical shape having alarge cylindrical wall thickness and a diameter smaller than that of theinlet communication portion 34. The inlet portion 36 is formedintegrally with the inlet communication portion 34 such that the inletportion 36 extends outwardly from a cylindrical wall of the inletcommunication portion 34. The inlet portion 36 communicates on its baseside opening (located near the inlet communication portion 34) with theinlet portion 34, while communicating at its open end portion with theexterior. This open end portion serves as an inlet 32 for introducingthe compressed air from the exterior into the filter device 10.

The outlet passage portion 24 consists of an outlet communicationportion 40 and an outlet portion 42. The outlet communication portion 40has a construction substantially identical with that of the inletcommunication portion 34, while the outlet portion 42 has a constructionsubstantially identical with that of the inlet portion 36. Each of theoutlet communication portion 40 and the outlet portion 42 takes asubstantially cylindrical shape having a large cylindrical wallthickness. The outlet communication portion 40 having a diameter largerthan that of the outlet portion 42 extends parallel to the axialdirection of the body 16, i.e., in the vertical direction as viewed inFIG. 3. The outlet communication portion 40 has an upper openingcommunicating with the exterior, and a lower opening communicating withthe second sleeve 28. The outlet portion 42 is formed integrally withthe outlet communication portion 40 such that the outlet portion 42communicates with the outlet communication portion 40 and such that theoutlet portion 42 extends outwardly from a cylindrical wall of theoutlet communication portion 40. The outlet portion 42 communicates atits open end portion with the exterior. This open end portion serves asan outlet 38 for feeding the compressed air out of the filter device 10to the exterior. A reference numeral 47 in FIGS. 3 and 4 designates ametallic connector, which is fixed in a hole of each of the inlet 32 andthe outlet 38, for connecting a suitable pipe with a corresponding oneof the inlet 32 and the outlet 38.

The thus constructed inlet passage portion 22 and the outlet passageportion 24 are arranged in parallel with each other such that the inlet32 and the outlet 38 extend in a direction perpendicular to the axialdirection of the body 16, and such that the inlet 32 and the outlet 38open in the opposite directions. A portion of the cylindrical wall ofthe inlet communication portion 34, which portion is radially remotefrom the inlet portion 36, is connected with a portion of thecylindrical wall of the outlet communication portion 40, which portionis radially remote from the outlet portion 42.

Thus, the inlet passage portion 22 and the outlet passage portion 24 areunited with each other. The first sleeve 26 communicates through theinlet passage portion 22 with the exterior, while the second sleeve 28communicates through the outlet passage portion 24 with the exterior.The inlet passage portion 22 has an inlet passage 37 formed therein, forintroducing the compressed air from the exterior into the first sleeve26 (the first filter means 12). The outlet passage portion 24 has anoutlet passage 39 formed therein, for feeding the compressed air outfrom the second sleeve 28 (the second filter means 14) to the exterior.

Each of the upper and lower openings of the inlet communication portion34 constituting the inlet passage portion 22 has an inside diametersubstantially equal to or slightly larger than that of the first sleeve26, while each of the upper and lower openings of the outletcommunication portion 40 constituting the outlet passage portion 24 hasan inside diameter substantially equal to or slightly larger than thatof the second sleeve 26. This dimensioning makes it possible to removeand introduce the first filter element 88 including a first packing 27and constituting the first filter means 12, through the upper and loweropenings of the inlet communication portion 34 from and into the body16, and also to remove and introduce the second filter element 90including a second packing 29 and constituting the second filter means14, through the upper and lower openings of the outlet communicationportion 40 from and into the body 16 (see FIG. 1). Thus, the upperopenings of the inlet communication portion 34 and the outletcommunication portion 40 function as access openings 41, 41 throughwhich the first and second elements 88, 90 are removed from andintroduced into the first and second sleeves 26, 28, respectively.

Each of the inlet communication portion 34 and the outlet communicationportion 40 includes a tapered portion 43 which is chamfered at the innerperiphery of a corresponding one of the access openings 41, 41 and aninternal thread portion 49 which is internally threaded and which isaxially adjacent to the tapered portion 43. The tapered portion 43 has adiameter which increases in the outward direction (upward direction).Further, the inlet communication portion 34 and the outlet communicationportion 40 are united at the outer peripheries of their upper endportions, with a generally rectangular plate-like flange 45 whichprotrudes outwardly from the outer peripheries of the inletcommunication portion 34 and the outlet communication portion 40 over apredetermined distance. Besides, each of the outer peripheries of lowerend and intermediate portions of the portions 34, 40 is provided with aconnecting rib 61.

Each of the first and second sleeves 26, 28 communicating with the inletcommunication portion 34 and the outlet communication portion 40,respectively, takes the form of a cylindrical shape. The height and theinside diameter of the first sleeve 26 are substantially equal to thoseof the second sleeve 28. The inside diameter of the first sleeves 26 issufficiently larger than that of the inlet 32, while the inside diameterof the second sleeves 28 is sufficiently larger than that of the outlet38. In other words, the cross sectional areas of fluid flow through thefirst and second sleeves 26, 28 are larger than the opening areas of theinlet 32 and the outlet 38, respectively. The thus constructed first andsecond sleeves 26, 28 are united with the inlet communication portion 34and the outlet communication portion 40, respectively, so as to extendparallel to each other in the axial direction of the body 16, from thelower ends of the inlet communication portion 34 and the outletcommunication portion 40, respectively. The first and second sleeves 26,28 communicate at their lower openings with the guide passage portion30.

The guide passage portion 30 communicating with the first and secondsleeves 26, 28 is a generally cup-shaped structure which issubstantially elliptical in horizontal cross section and whose depth islarger than the respective inside diameters of the first and secondsleeves 26, 28. Further, the guide passage portion 30 has an outwardlybulging bottom portion 48 having a substantially semi-spherical shape.The bulging bottom portion 48 has a through-hole 50 formed through itsbottom wall in communication with the exterior. According to theabove-described arrangement, the first and second sleeves 26, 28communicate with each other through the guide passage portion 30 havinga cross sectional area larger than that of the first and second sleeves26, 28. Thus, the guide passage portion 30 provides a guide passage 44,so that the compressed air is introduced from the first sleeve 26 to thesecond sleeve 28 through this guide passage 44. The guide passage 44communicates with the exterior through the through-hole 50 formedthrough a bottom portion of the guide passage portion 30.

The guide passage portion 30 has a flange 54 integrally formed at alower end portion of the bulging bottom portion 48 such that the flange54 extends outwardly from an outer surface of the bottom portion 48. Onthe flange 54, there are formed six bolt-hole portions 52 which arespaced apart from each other in a circumferential direction of theflange 54 at a predetermined spacing interval. The six bolt-holeportions 52 receive suitable bolts for fixedly attaching the drain unit20 to the guide passage portion 30. Among the six bolt-hole portions 52,predetermined two bolt-hole portions has respective metallic connectors56, 56 fixedly received therein, for engagement with the bolts. Further,the guide passage portion 30 has two reinforcing ribs 53, 53 and eightreinforcing ribs 55 formed integrally therewith. One of the tworeinforcing ribs 53, 53 is formed on an upper end portion of acylindrical wall of the guide passage portion 30 so as to extend in acircumferential direction of the guide passage portion 30, while theother of the reinforcing ribs 53, 53 is formed on an intermediateportion of the cylindrical wall of the guide passage portion 30 so as toextend in the circumferential direction of the guide passage portion 30.Each of the eight reinforcing ribs 55 extends in a depth (height)direction of the guide passage portion 30 from the reinforcing rib 53 tothe connecting rib 54. Thus, the guide passage portion 30 is reinforcedby the ribs 53, 55.

The inlet passage portion 22, the outlet passage portion 24, the firstand second sleeves 26, 28 and the guide passage portion 30 which areconstructed as described above are integrally formed of a transparentsynthetic resin such as polycarbonate, polyethylene terephthalate andpolyamide, whereby the body 16 is formed as a one-piece molding of thetransparent synthetic resin.

Like the body 16, the caps 18, 18 which are attached to the top of thebody 16 are formed of a synthetic resin such as polycarbonate,polyethylene terephthalate and polyamide. As shown in FIGS. 8-10, eachof the caps 18, 18 consists of a threaded portion 64, a disc-like holdportion 65, a knob portion 66 and three legs 68. The threaded portion 64takes a generally cylindrical shape and is integrally formed on a lowerface of the hold portion 65. The threaded portion 64 has an externalthread formed on its outer circumferential surface and a criss-crossreinforcing rib integrally formed in its interior. The knob portion 66is integrally formed on an upper face of the hold portion 65, and takesa generally rectangular plate-like shape having a generally arcuateupper side. The three legs 68 are integrally formed on a lower face ofthe threaded portion 64, and are equi-angularly spaced apart from eachother in a circumferential direction of the threaded portion 64. Each ofthe three legs 68 has predetermined length and width and extendsdownwardly from an outer peripheral portion of the lower face of thethreaded portion 64. One of the three legs 68 is located right below oneof the longitudinal end portions of the knob portion 66, whereby thethree legs 68 are arranged symmetrically with respect to a plane whichpasses a center of the hold portion 65 and which is parallel to aprincipal plane of the knob portion 66.

The drain unit 20 which is to be attached to the bottom of the body 16is formed of the same synthetic resin as the body 16 and the caps 18,18. The drain unit 20 is a generally cup-shaped member having a smallwall thickness, and opens upwardly, as shown in FIGS. 11 and 12. Acylindrical wall of the drain unit 20 includes a thick-walled portion 72at its upper end portion. The thick-walled portion 72 has a thicknesslarger than that of the rest of the cylindrical wall by a predeterminedamount, and protrudes outwardly. Thus, the outside diameter of thethick-walled portion 72 is substantially equal to or slightly smallerthan the inside diameter of the through-hole 50 which is formed throughthe bottom portion of the guide passage portion 30. On an upper portionof the thick-walled portion 72, there is formed a square groove 78extending in a circumferential direction of the drain unit 20 and havinga predetermined depth. On a lower portion of the thick-walled portion72, there is integrally formed an outwardly projecting flange 73. Thereare six bolt-hole portions 74 formed on the flange 73 and equi-angularlyspaced apart from each other in the circumferential direction of thedrain unit 20. The six bolt-hole portions 74 are connected with eachother through a connecting rib 76 extending in the circumferentialdirection of the drain unit 20 and formed integrally with the sixbolt-hole portions 74. The six bolt-hole portions 74 receive suitablebolts for fixedly attaching the drain unit 20 to the guide passageportion 30.

Further, there are six reinforcing ribs 80 integrally formed on an outercircumferential surface of the above-indicated rest of the cylindricalwall of the drain unit 20. The six reinforcing ribs 80 extend verticallyfrom the flange portion 73 toward a bottom wall of the drain unit 20,and are equi-angularly spaced apart from each other, for therebyreinforcing the flange portion 73 and the cylindrical wall of the drainunit 20. A reference numeral 70 in FIGS. 11 and 12 designates athrough-hole for receiving a drain valve of an automatic draining device84 accommodated in the drain unit 20, as described below.

As is apparent from FIGS. 1 and 2, the drain unit 20 constructed asdescribed above is attached to the guide passage portion 30 of the body16, while the caps 18, 18 are attached to the respective access openings41, 41 formed in the inlet passage portion 22 and the outlet passageportion 24 constituting the inlet passage 37 and the outlet passage 39,respectively, after the first and second filter elements 88, 90constructed as described below have been accommodated in the first andsecond sleeves 26, 28 of the body 16, respectively. Thus, the filterdevice for compressed air 10 is assembled.

More specifically described, after the automatic draining device 84 hasbeen accommodated in the drain unit 20, the drain unit 20 is attached tothe body 16, with an O-ring 86 being disposed in the square groove 78formed in the outer circumferential surface of the upper end portion(the thick-walled portion 72) of the cylindrical wall of the drain unit20, such that the upper end portion (the thick-walled portion 72) isfitted in the through-hole 50 formed through the bottom of the bulgingbottom portion 48 of the guide passage portion 30 of the body 16, andsuch that the six bolt-hole portions 74 formed on the flange 73 arelocated in alignment and abutting contact with the six bolt-holeportions 52 formed on the flange 54 of the guide passage portion 30 ofthe body 16. A suitable bolt is inserted into each of six holes whichare provided by the alignment of the six pairs of bolt-hole portions 52,72, and is screwed into a suitable nut or into the metallic connector 56fixedly received in the bolt-hole portions 52. Thus, the drain unit 20having the automatic draining device 84 accommodated therein is attachedto the bottom of the bulging bottom portion 48 of the guide passageportion 30 of the body 16, with the through-hole 50 being fluid-tightlyclosed.

On the other hand, the first filter element 88 including the firstpacking 27 and the second filter element 90 including the second packing29 are accommodated in the first and second sleeves 26, 28,respectively, such that each of the first and second filter elements 88,90 is engaged with a corresponding one of shoulder portions 46, 46 whichare formed at upper opening portions of the respective sleeves 26, 28and a corresponding one of shoulder portions 51, 51 which are formed atlower opening portions of the respective sleeves 26, 28, whereby thefirst and second filter means 12, 14 are constituted.

More specifically described, the first filter element 88 consists of thefirst packing 27, upper and lower retainer plates 57, 59, and a core bar92, as shown in FIGS. 13 and 14. The core bar 92 has a key ring 104 atone of opposite ends thereof. The first packing 27 is fixedly wound onthe core bar 92 which passes through and engages the upper and lowerretainer plates 57, 59. The upper and lower retainer plates 57 are heldin abutting contacts with the first packing 27 at upper and lower facesof the first packing 27, respectively, as viewed in FIG. 13.

More described in detail, the core bar 92 consists of a body 102 and thekey ring 104. The core bar body 102 is integrally formed of the samesynthetic resin as used for forming the body 16, the caps 18, 18 and thedrain unit 20, and consists of a substantially U-shaped end portion 94,a long column-like intermediate portion 96 having a substantiallyrectangular cross sectional shape and a disc-like end portion 100 havinga through-hole 98 formed through its center. The key ring 104 serves asa pull tab, and is a coil consisting of about two turns of a wire madeof a suitable material such as stainless steel and having apredetermined diameter. The key ring 104 passes through the through-hole98 such that a longitudinal direction of the key ring 104 as seen in theelevational view of FIG. 13 is substantially aligned with an axialdirection of the core bar body 102. The U-shaped end portion 94 has twoengaging portions 106, 106 formed at a substantially axiallyintermediate position thereof such that the engaging portions 106, 106extend outwardly. The intermediate portion 96 has, on its side faces,substantially rectangular pyramid-like protrusions 108 which are spacedapart from each other at a predetermined spacing interval. However, theprotrusions 108 do not have to be necessarily provided. The key ring 104passing through the through-hole 98 has circumferentially opposite endsof the coil which are held in contacts with the respective principalfaces of the end portion 100 under pressure produced by its elasticity,whereby the rotation of the key ring 104 about the through-hole 98 isprevented.

The first packing 27 of the first filter means 12 is a metallic-fiberaggregation which is formed by randomly aggregating a large number ofshort fibers or long fibers 58 made of stainless steel fibers or othermetallic materials, such that about 90% of the short fibers or longfibers 58 extend in a direction perpendicular to the winding directionof the metallic-fiber aggregation, while about 10% of the short fibersor long fibers 58 extend in the other directions. As shown in FIG. 15,the large number of the short and long fibers 58 are complicatedlytangled with each other, so as to constitute a sheet-like fabric 60having a predetermined thickness. The sheet-like fabric 60 is wound onthe core bar 62 such that the sheet-like fabric 60 is engaged with theprotrusions 108 at an end portion thereof, so that the fabric 60 takesthe form of a substantially cylindrical roll corresponding to aninternal shape of the first sleeve 29. The fabric 60 in the form of theroll is then wrapped by a film 110 made of a transparent syntheticresin, and is kept in the roll form by three pins provided at respectivepositions on the outer circumferential surface of the roll so as to fixthe fabric 60 to the core bar 92.

The upper retainer plate 57 engages the core bar 92 such that the corebar 92 passes through the retainer plate 57, and is held in abuttingcontact with the upper face of the first packing 27, as viewed in FIG.13. The upper retainer plate 57 takes a stepped disc-like shape having astepped portion 116. The stepped portion 116 takes a shape correspondingto the shoulder portions 46, 46 which are formed at the upper openingportions of the respective first and second sleeves 26, 28. The upperretainer plate 57 has a center hole 112 having a substantiallyrectangular cross sectional shape and formed through a center of theupper retainer plate 57. Through the center hole 112, the body 102 ofthe core bar 92 is passed. The upper retainer plate 57 further has aplurality of through-holes 114 formed through a portion around thecenter hole 112 so as to permit the compressed air to flow through thethrough-holes 114. On the other hand, the lower retainer plate 59 whichis held in abutting contact with the lower face of the first packing 27,as viewed in FIG. 13, takes a stepped disc-like shape having a steppedportion 118. The stepped portion 118 has a shape corresponding to theshoulder portions 51, 51 which are formed at the lower opening portionsof the respective first and second sleeves 26, 28. Like the upperretainer plate 57, the lower retainer plate 59 has a center hole 120which has a substantially rectangular cross sectional shape and aplurality of through-holes 122 through which the compressed air ispermitted to flow. As is apparent from FIG. 14, the upper retainer plate57 engages the key ring 104 of the core bar 92, while the lower retainerplate 59 engages the engaging portions 106, 106 of the core bar 92. Theengaging portions 106, 106 which are formed on the U-shaped end portion94 and which project from the U-shaped end portion 94 are passed throughthe center hole 120 such that the U-shaped end portion 94 is deformedinwardly. The U-shaped end portion 94 is then restored to its originalshape owing to its elasticity after the engaging portions 106 have beenpassed through the center hole 120, whereby the lower retainer plate 59is engaged with the engaging portions 106, 106 of the core bar 92.

The thus constructed first filter element 88 is prepared as shown inFIGS. 15 and 16. First, the core bar body 102 is positioned at onelongitudinal end of the sheet-like fabric 60 having predetermined widthand length, such that the longitudinal end portion of the fabric 60engages the substantially rectangular pyramid-like protrusions 108 whichare formed on the side faces of the intermediate portion 96 of the corebar body 102. The core bar body 102 is then rolled so that apredetermined length of the sheet-like fabric 60 is wound on the corebar body 102. Then, the transparent synthetic resin-made film 110 isdisposed on the outer surface of the unwound portion of the sheet-likefabric 60, and the unwound portion is wound so as to form a first roll124 wrapped by the film 110 on its outer circumferential surface.

Subsequently, the first roll 124 is adjusted to have a predeterminedoutside diameter by a suitable method, for example, by introducing thefirst roll 124 into a suitable cylindrical case having a predeterminedinside diameter. Then, the first roll 124 receives three pins 126provided at the respective positions at an end portion of the film 110,as shown in FIG. 16, so that the first roll 124 maintains a cylindricalshape having an outside diameter substantially equal to thepredetermined outside diameter. Then, the lower retainer plate 59 isattached to the core bar body 102 constituting the first roll 124 suchthat the center hole 120 of the lower retainer plate 59 is engaged withthe engaging portions 106, 106 of the core bar body 102, and the endportion 100 of the core bar body 102 is passed through the center hole112 of the upper retainer plate 57. Then, the key ring 104 is passedthrough the through-hole 98 formed through the end portion 100 of thecore bar body 102. Thus, the upper retainer plate 57 is attached to thecore bar 92, and the first filter element 88 is completed.

On the other hand, the second filter element 90 which includes thesecond packing 29 and which is accommodated in the second sleeve toconstitute the second filter means 14 is prepared according to aprocedure shown in FIGS. 17 and 18. The second filter element 90includes the second packing 29 which is a belt-like fabric mesh formedof cotton fibers as in the conventional filter device, and is notprovided with the film 110 for holding the shape, unlike the firstfilter element 88. In the other aspects, however, the second filterelement 90 is substantially identical with the first filter element 88.

That is, as shown in FIG. 17, the core bar body 102 is positioned at onelongitudinal end of a belt-like fabric mesh 128 formed of cotton fibersand having predetermined width and length, such that the longitudinalend portion of the fabric mesh 128 engages the substantially rectangularpyramid-like protrusions 108 which are formed on the side faces of theintermediate portion 96. The core bar body 102 is then rolled so thatthe fabric mesh 128 is wound on the core bar body 102 for therebyforming a second roll 130. Subsequently, the second roll 130 is adjustedto have a predetermined outside diameter by the same method as adoptedfor the first roll 124, and the second roll 130 receives three pins 126provided at the respective positions at an end portion of the fabricmesh 128, as shown in FIG. 18, so that the second roll 124 keeps acylindrical shape having an outside diameter substantially equal to thepredetermined outside diameter. Then, as in the case of the first filterelement 88, the lower retainer plate 59 and the upper retainer plate 57are engaged with the core bar 92 at the respective predeterminedpositions of the core bar 92, whereby the second filter element 90 iscompleted.

The first and second filter elements 88, 90 having the constructions asdescribed above are accommodated in the first and second sleeves 26, 28,respectively, such that the stepped portions 116, 118 of the upper andlower retainer plates 57, 59 constituting each of the filter elements88, 90 are engaged with the shoulder portions 46, 50 of the body 16.Then, the caps 18, 18 are attached to the respective access openings 41,41 which are formed in the body 16 at the inlet passage portion 22 andthe outlet passage portion 24 constituting the inlet passage 37 and theoutlet passage 39, respectively.

More specifically described, each of the caps 18, 18 is screwed to thecorresponding one of the access openings 41, 41 such that an externalthread formed portion of the threaded portion 64 is engaged with thecorresponding one of the internal thread portions 49, 49 which areformed in the inlet communication portion 34 and the outletcommunication portion 40, and such that the three legs 68 of each of thecaps 18, 18 are inserted into the corresponding one of the inletcommunication portion 34 of the inlet passage portion 22 and the outletcommunication portion 40 of the outlet passage portion 24, while anO-ring 82 is interposed between the disc-like hold portion 65 and thetapered portion 43 of the access opening 41. Thus, the caps 18, 18 arefluid-tightly and removably attached to the respective access openings41, 41 which are the upper openings of the inlet communication portion34 and the outlet communication portion 40.

In the present embodiment, the caps 18, 18 are attached to therespective access openings 41, 41 formed in the body 16 as describedabove such that one of the three legs 68 which is located right belowone of the longitudinal end portions of the knob portion 66 is mostdistant from the inlet 32 or the outlet 38, whereby the longitudinaldirection of the knob portion 66 is parallel to the opening direction ofthe inlet 32 or the outlet 38 while the other two legs 68, 68 arelocated symmetrically with each other such that the two legs 68, 68 arenot exposed to the inlet 32 or the outlet 38. Further, with the caps 18,18 attached to the body 16 as described above, the three legs 68 of eachof the caps 18, 18 inserted into the corresponding one of the inletcommunication portion 34 and the outlet communication 40 are held attheir ends in abutting contact with the corresponding one of the upperretainer plates 57 fitted in the upper openings of the first and secondsleeves 26, 28, with a predetermined abutting force. This arrangementprevents upward movements of the upper retainer plates 57 and the filterelements 88, 90, while each of the first and second filter elements 88,90 is interposed and gripped by and between the legs 68 and the lowerretainer plate 59 which is engaged with the shoulder portion 51.

The caps 18, 18 and the drain unit 20 are attached to the body 16 withthe first and second filter elements 88, 90 being accommodated in thefirst and second sleeves 26, 28, respectively, as described above, tocomplete the filter device 10 for compressed air, wherein only the inlet32 and the outlet 38 are open to the exterior, and wherein thecompressed air entering the inlet passage portion 22 via the inlet 32 ispassed through the first filter means 12, the guide passage portion 30and the second filter means 14 into the outlet passage portion 24, andis then fed out via the outlet 38. Thus, a fluid passage for thecompressed air is formed through the filter device 90.

In the thus constructed filter device 10 for compressed air, vaporand/or liquid particles remaining in the compressed air are separatedand removed from the compressed air, as described below.

First, the compressed air supplied through the inlet 32 is introducedthrough the inlet passage 37 formed in the inlet passage portion 22,into the first filer means 12 having a large cross sectional area. Asthe compressed air is passed through the first filter means 12, thevapor and/or the liquid particles such as water and oil contained in thecompressed air are condensed or coalesced into liquid drops, by aneffect of adiabatic expansion, or by an increased capture effect as aresult of a reduced velocity of flow of the compressed air throughthe-first filter means 12, so as to be separated from the compressedair.

Subsequently, as the compressed air which has passed through the firstfilter means 12 is introduced into the guide passage 44 formed in theguide passage portion 30, the vapor and/or the liquid particles arefurther condensed or coalesced by further adiabatic expansion or anincreased capture effect as a result of further reduction of flowvelocity of the compressed air in the guide passage portion 30, sincethe cross sectional area of the guide passage portion 30 is made largerthan that of the first filter means 12.

The liquid drops, which have been produced by the above condensation orcoalescence in the guide passage portion 30, or produced by thecondensation or coalescence in the first filter means 12 and broughtinto the guide passage portion 30 by the flow of the compressed air, areeffectively separated from the compressed air as a result of the reducedflow velocity of the compressed air, as the compressed air is introducedinto the guide passage portion 30 whose cross sectional area is larger.And the separated liquid drops are dropped by gravity, through thethrough-hole 50 into the drain unit 20 attached to the bottom portion ofthe guide passage portion 30. In this case, some of the liquid drops maystick to the first packing 27 of the first filter means 12, withoutbeing brought into the guide passage portion 30 by the flow of thecompressed air. Even these liquid drops are dropped through the guidepassage portion 30 into the drain unit 20, due to their own weight. Theliquid drops, which have been dropped into the drain unit 20 asdescribed above, are discharged through the automatic draining device 84to the exterior.

The compressed air, from which the vapor and/or the liquid particleshave been separated and removed as described above, is introduced intothe second filter means 14 whose cross sectional area is smaller thanthat of the guide passage portion 30, so that the compressed air issubject to the effect of the adiabatic expansion, or an evaporationeffect as a result of an increased velocity of flow of the compressedair through the second filter means 14. Further, as the compressed airis passed through the second packing 29 of the second filter means 14,water and/or oil in the form of liquid particles remaining in thecompressed air is evaporated by an effect of whirlpool phenomenon of theair flow, or is absorbed by the second packing 29, while dust in theform of solid particles remaining in the compressed air is captured bythe second packing 29.

As a consequence, the compressed air which has been fed out from theoutlet 38 through the outlet passage 39 formed in the outlet passageportion 24 does not contain the liquid and solid particles such as thewater and oil.

As described above, the filter device 10 for compressed air according tothe present embodiment is constructed such that the compressed airintroduced through the inlet passage 37 into the body 16 is furtherintroduced into the first filter means 12 so as to be passed through thefirst packing 27 of the first filter means 12, and is then introducedthrough the guide passage 44 into the second filter means 14 so as to bepassed through the second packing 29 of the second filter means 14, sothat the compressed air is cleaned and dried with substantially completeremoval of the liquid particles such as water and oil and the solidparticles such as dust.

The present filter device 10 having such a good filtering performance isconstructed such that the first and second sleeves 26, 28 accommodatingthe first and second filter elements 88, 90 therein and constituting thefirst and second filter means 12, 14, respectively, the inlet passageportion 22 defining the inlet passage 37, the guide passage portion 30defining the guide passage 44 and the outlet passage portion 24 definingthe outlet passage 39 are integrated with each other to form the body 16as a single unit, such that the access openings 41, 41 are formed at theinlet passage portion 22 and the outlet passage portion 24 so as toremove the first and second packings 27, 29 through the access openings41, 41, and such that the caps 18, 18 are fluid-tightly and removablyattached to the respective access openings 41, 41. Unlike theconventional filter device, therefore, the present filter device 10 doesnot require time-consuming operations such as disassembling of thefilter device 10 into its component parts, upon replacing the first andsecond packings 27, 29 clogged with dust and/or grease. In the presentfilter device 10, the access openings 41, 41 can be opened by simplyremoving the caps 18, 18, so that the first and second filter elements88, 90 are easily exposed to the exterior. Each of the first and secondfilter elements 88, 90 consists of the core bar 92 having the key ring104 at its end portion, the corresponding one of the first and secondpackings 27, 29 each fixedly wound on the core bar 92, and the upper andlower retainer plates 57, 59 engaged with the core bar 92 and held inabutting contact with the axial opposite ends of the corresponding oneof the first and second packings 27, 29, as described above.Accordingly, the first and second filter elements 88, 90 including theclogged first and second packings 27, 29 can be removed from the firstand second sleeves 26, 28 to the exterior of the body 16 through theaccess openings 41, 41 from which the caps 18, 18 have been removed, bysimply pulling the core bar 92 of the first or second filter elementwith the fingers holding the key ring 104. Clean first and secondpackings 27, 29 together with the other components of the first andsecond filter elements 88, 90 can be accommodated in the first andsecond sleeves 26, 28 by pushing the sleeves 26, 28 at the key ring 104.After the replacement of the packings 27, 29, all that has to be done isto simply attach the caps 41 to the access openings 41. Thus, it is notnecessary to carry out a conventionally required cumbersome operationsuch as re-assembling the component parts.

Further, the present filter device 10 is constructed such that each ofthe caps 18, 18 attached to the body 16 consists of the knob portion 66,the hold portion 65 and the threaded portion 64, so that the caps 18, 18are removably attached to the access openings 41, 41 by engagement ofthe threaded portions 64 having the respective external threads with theinternal thread portions 49 formed on the inlet communication portion 34and the outlet communication portion 40. According to this construction,it is possible to rotate the caps 18, 18 relative to the respectiveaccess openings 41, 41 through the knob portion 66 without using aparticular tool, so as to easily attach and remove the caps 18, 18 toand from the access openings 41, 41. Further, since the knob portion 66has a generally rectangular plate-like shape having a generally arcuateupper surface, a torque can be easily applied to the cap 18 by the thumband the index finger holding the holding portion 65, furtherfacilitating the operator to attach and remove the cap 18.

In the filter device 10 according to the present embodiment, therefore,the first and second packings 27, 29 of the first and second filtermeans 12, 14 can be very easily and quickly replaced without anycumbersome and time-consuming operation, which is required in theconventional device.

Further, in the above-described filter device 10, the core bar 92constituting each one of the first and second filter elements 88, 90constructed as described above can be formed of a material such as asynthetic resin, together with the retainer plates 57, 59, by a singlemold. Thus, the present filter device 10 can be produced without aconsiderable increase in the cost required for the production,advantageously avoiding an increase in the production cost. The key ring104 constituting the core bar 92 is passed through the through-hole 98formed through the end portion 100 of the core bar body 102 such thatthe longitudinal direction of the key ring 104 is substantially alignedwith the axial direction of the core bar body 102, as seen theelevational view of FIG. 13. Further, since the key ring 104 isprevented form rotating about the through-hole 98, the key ring 104 isprevented from falling down in the inlet passage 37 or outlet passage 39of the filter device 10. As a result, the replacement of the first andsecond packings 27, 29 can be made more easily and quickly.

Besides, in the filter device 10 according to the present embodiment,the sheet-like fabric 60 which is formed of the large number of shortfibers or long fibers 58 made of stainless steel fibers or othermetallic materials and which is the first packing 27 of the first filterelement 88 is wound on the core bar 92 as a cylindrical roll, andreceives the pins 126 through the film 110 made of a transparentsynthetic resin provided at the respective positions of the outercircumferential surface of the roll, so as to be fixed to the core bar92. This construction makes it possible to keep the cylindrical shape ofthe sheet-like fabric 60, which is generally difficult, and toeffectively prevent the short fibers or long fibers 58 made of metallicmaterials from dropping into the guide passage 44.

Further, since the present filter device 10 is constructed, as describedabove, such that the first and second sleeves 26, 28, the inlet passageportion 22, the guide passage portion 30 and the outlet passage portion24 are integrated with each other to form the body 16 as a single unit,the present filter device 10 assures a remarkable increase influid-tightness reliability, as compared with that of the conventionaldevice wherein separate parts are connected by bolts through suitablepackings.

Further, in the filter device 10 according to the present embodiment, byattaching the caps 18, 18 to the respective access openings 41, 41, thethree legs 68 of each of the caps 18, 18 inserted into the correspondingone of the inlet communication portion 34 and the outlet communication40 is brought into abutting contact at its end with the correspondingone of the upper retainer plates 57, 57 of the first and second filterelements 88, 90 accommodated in the first and second sleeves 26, 28,with a predetermined abutting force. This arrangement does not requireany complicated devices to prevent upward movements of the upperretainer plates 57, 57 and the filter elements 88, 90, while the firstand second filter elements 88, 90 are interposed and gripped by andbetween the legs 68 and the lower retainer plates 59 which are engagedwith the lower shoulder portions 51 of the body 16. Accordingly, thearrangement effectively prevents movements of the first and secondpackings 27, 29 constituting the first and second filter elements 88, 90in the body 16, which movements may be caused by, for example, flows ofthe compressed air. The abutting force produced by the legs 68 of thecap 18 with respect to the retainer plate 57 is released by removing thecap 18 from the body. Therefore, the thus constructed mechanism forpreventing the upward movements of the filter elements 88, 90 does notdeteriorate the operation for replacing the first and second packings27, 29.

Further, in the filter device 10 according to the present embodiment,the three legs 68 of the cap 18 attached to the body 16 are formed onthe outer peripheral portion of the lower face of the threaded portion64 such that the three legs 68 are equally spaced apart from each otherin the circumferential direction of the threaded portion 64, and suchthat the three legs 68 are arranged symmetrically with respect to aplane which passes the center of the hold portion 65 and which isparallel to the principal plane of the knob portion 66. The caps 18, 18are attached to the respective access openings 41, 41 formed in the body16 such that one of the three legs 68 which is located right below oneof the opposite longitudinal end portions of the knob portion 66 is mostdistant from the corresponding one of the inlet 32 and the outlet 38,whereby the longitudinal direction of the knob portion 66 is parallel tothe opening direction of the inlet 32 or the outlet 38 while the othertwo legs 68, 68 are located symmetrically with each other such that thetwo legs 68, 68 are not exposed to the inlet 32 or the outlet 38.Therefore, any one of the three legs 68 does not give a considerableresistance to the flow of the compressed air, whereby an increase in thepressure loss which is caused by the provision of the legs 68 to the cap18 is minimized in the filter device 10. Further, upon attaching thecaps 18, 18 to the body 16, it is possible to minimize the pressure lossand to easily prevent a leakage of the compressed air into the body 16due to insufficient screwing of the caps 18, 18, by merely aligning thelongitudinal direction of the knob portion 66 with the opening directionof the inlet 32 or the outlet 38.

Further, the present filter device 10 according to the presentembodiment is constructed such that the access openings 41, 41 closed bythe caps 18, 18 are defined by the respective upper openings of theinlet and outlet passage portions 22, 24, which constitute the inlet andoutlet passages 37, 39, for introducing the compressed air into the body16 and feeding out the compressed air to the exterior, respectively.According to this arrangement, even if the compressed air leaks out fromthe body 16 through the access openings 41, 41, the air leakage has acomparatively small influence on the flow velocity and the pressure ofthe compressed air flowing through the first and second sleeves 26, 28and the guide passage portion 30, as compared with an arrangementwherein the compressed air may leak through the first sleeve 26 and/orsecond sleeve 28 and/or the guide passage portion 30. Accordingly, thepresent arrangement prevents or minimizes deterioration of the filteringperformance of the first and second filter means 12, 14.

Further, in the present filter device 10 according to the presentembodiment, wherein the body 16 is made of the transparent syntheticresin, the state of clogging of the first and second packings 27, 29with dust and/or grease can be observed through the transparent body 16,making it easy to know a time of replacement of the packings 27, 29.

Further, in the present filter device 10, the first packing 27 of thefirst filter means 12 is a metallic-fiber aggregation which is formed byrandomly aggregating a large number of short or long fibers 58 made ofmetallic materials. Therefore, it is not necessary to weave or knit themetallic fibers 58, as required for the conventional device, for formingthe first packing 27, so that the first packing 27 can be formed withimproved efficiency and at a reduced cost. Besides, the first packing 27is constituted by a comparatively small amount of the metallic fibers58, but has a fiber destiny which is equal to or higher than the oneemployed in the conventional device. Thus, the first filter means 12assures an excellent performance in the condensation and/or coalescenceof the vapor and/or liquid particles, and has a reduced weight, leadingto a reduced weight of the filter device 10, and a reduced material costowing to the reduced amount of the metallic fibers 58.

Further, in the present filter device 10 according to the presentembodiment, the sheet-like fabric 60 as the first packing 27 is ametallic-fiber aggregation which is formed by randomly aggregating thelarge number of short or long fibers 58 made of stainless steel fibersor other metallic materials such that about 90% of the short or longfibers 58 extend in a direction perpendicular to the winding directionof the metallic-fiber aggregation, while about 10% of the short or longfibers 58 extend in the other directions. Therefore, the sheet-likefabric 60 has a comparatively small flexural strength in the windingdirection, facilitating operation for winding the sheet-like fabric 60on the core bar 92, whereby the required cost for the production of thefilter device 10 is further reduced.

While there has been described one embodiment of the present invention,for illustrative purpose only, it is to be understood that the inventionis not limited to the details of the described embodiment.

For example, in the above-described embodiment, the core bar 92constituting each of the first and second filter elements 88, 90consists of the core bar body 102 and the key ring 102 serving as thepull tab. However, the core bar body and the pull ring may be formedintegrally with each other. Besides, the shapes of the core bar 92 andthe retainer plates 57, 59 are not limited to those in theabove-described embodiment. Further, the construction for engagement ofthe retainer plates 57, 59 with the core bar 92 is not limited to thatin the above-described embodiment, either, and a well-known constructionfor engagement may be suitably employed.

In the above-described embodiment, the body 16 is integrally formed of atransparent synthetic resin such as polycarbonate, polyethyleneterephthalate and polyamide. However, any other kinds of synthetic resinmaterials may be selected as needed by taking account of a desiredstrength of the body 16.

In the above-described embodiment, the wound first packing 27 of thefirst filter element 88 is wrapped by the film 110 made of a syntheticresin over its outer circumferential surface. However, the film 110 doesnot have to be necessarily provided on the first packing 27. Where thebody 16 is made of a non-transparent material, the film 110 may bereplaced by a tubular body made of aluminum or other metallic materialsand having a thickness of about 0.5-1.0 mm, so that the tubular body isfitted on the outer circumferential surface of the first packing 27,whereby the tubular body cooperates with the first sleeve 26 toconstitute a dual safety structure for protecting the sleeve 26 of thebody 16 from bursting due to the compressed air. It is to be understoodthat the thus constructed tubular body made of a metallic material maybe applied also to the second filter element 90.

Additionally, a film made of a synthetic resin and having a thickness ofabout 0.5-1.0 mm may be formed at least on the outer circumferentialsurfaces of the first and second sleeves 26, 28, or preferably may beformed not only on the outer circumferential surfaces of the sleeves 26,28 but also on an outer circumferential surface of the guide passageportion 30 other than a portion thereof which is in abutting contactwith the drain unit 20, by a well-known method, for example, by applyingheat to the film so as to contract the film. This constructionalleviates an impact which may be given to the body 16 from theexterior, and also prevents scattering of broken pieces in the event ofbreakage of the body 16.

In the above-described embodiment, the first packing 27 of the firstfilter means 12 is a metallic-fiber aggregation which is formed byrandomly aggregating the large number of short or long fibers 58 made ofstainless steel fibers or other metallic materials such that about 90%of the short or long fibers 58 extend in a direction perpendicular tothe winding direction of the metallic-fiber aggregation, while about 10%of the short or long fibers 58 extend in the other directions. The largenumber of short or long fibers 58 are complicatedly tangled with eachother, so as to constitute a sheet-like fabric 60 having a predeterminedthickness. However, the first packing 27 may have other structure. Forexample, the first packing 27 may be a metallic-fiber aggregation whichis formed by randomly aggregating a large number of short or long fibers58 without any predetermined orientation. Further, a random aggregationof the metallic fibers 58 which does not have a specific form can besuitably used together with the above-described film 110, as the firstpacking 27. If the metallic fiber aggregation not having a specific formis used as the first packing 27, an operation required for forming thefirst packing 27 into the desired form can be eliminated, making itpossible to effectively simplify the production process of the firstfilter means 12 or the filter device 10. Further, the first packing 27may be a roll of a wire mesh fabric formed by weaving or knittingsuitable metallic steel fibers, or alternatively, a roll of mesh fabricformed by obliquely intersecting and bonding linear synthetic resinsdiagonally with each other.

Similarly, the second packing 29 of the second filter means 14 is notlimited to the belt-like fabric mesh formed of cotton fibers. A knownmaterial may be suitably used for the second packing 29.

Further, in the above-described embodiment, the automatic drainingdevice 84 having a known structure is provided in the drain unit 20, sothat the liquid, which has dropped and been stored in the drain unit 20is discharged into the exterior. However, this automatic draining device84 may be replaced by a known weep valve 102 or any one of known draindevices.

Still further, in the above-described embodiment in which the caps 18,18 as the closure members are screwed to the access openings 41, 41 withthe O-rings 82 interposed therebetween, the construction for attachingthe closure members is not limited to that of the embodiment, providedthe closure members fluid-tightly close the access openings and areremovable from the access openings.

Further, in the above-described embodiment, each of the caps 18, 18 isprovided with the three legs 68 formed integrally with the cap 18. Thethree legs 68 are held in abutting contact with the corresponding one ofthe upper retainer plates 57, 57 of the first and second filter elements88, 90 accommodated in the first and second sleeves 26, 28, with apredetermined abutting force, whereby the upward movements of the upperretainer plates 57, 57 and the filter elements 88, 90 are prevented, andeach of the first and second filter elements 88, 90 is interposed andgripped by and between the legs 68 and the lower retainer plate 59,which is engaged with the shoulder portion 51, so as to be fixedlyaccommodated in the first or second sleeve 26, 28. However, the numberand the shapes of the legs 68 are not limited to those of theembodiment, and the legs 68 do not have to be necessarily provided wheresome other fixing means is provided.

Further, it is to be understood that the entire shape of the filterdevice, the shapes of the closure members, the drain unit, and the othercomponents of the device are not limited to those of the describedembodiment.

It is to be understood that the present invention may be embodied withvarious other changes, modifications and improvements, which may occurto those skilled in the art, without departing from the spirit of theinvention.

As is apparent from the foregoing explanation, the filter device forcompressed air according to the present invention is constructed suchthat all the parts cooperating to form a fluid passage in the filterdevice are formed of a synthetic resin, integrally with each other so asto constitute a body of the filter device. The body is provided withaccess openings through which the first and second packings are removed.Further, the closure member is removably attached to each of the accessopenings so as to fluid-tightly close the access openings. According tothe present filter device, therefore, for replacing the clogged firstand second packings, it is not necessary to carry out time-consumingoperations such as disassembling of the filter device into the componentparts and an reassembling of the parts into the device. In the presentfilter device, the access openings are easily opened and closed, bysimply removing the caps from the respective access openings andre-attaching the caps to the respective access openings, so that thefirst and second packings are easily exposed to the exterior. Further,each of the first and second filter elements is constituted such thatthe two retainer plates are disposed on the axially opposite ends of thecorresponding one of the first and second packings, and such that thecore bar axially passing the center of the corresponding one of thefirst and second packings is engaged with the two retainer plates at theopposite end portions of the core bar and is provided with the pull tabat one of the opposite end portions, so that the filter elements can beremoved from and introduced into the first and second sleeves,respectively, by holding the pull tab. Accordingly, the first and secondpackings together with the other components of the first and secondfilter elements can be removed from and introduced into theabove-described body through the respective access openings which areopened by removing the closure members from the access openings, withouta necessity of using a tool. Thus, the removal and introduction of thefirst and second packings from and into the body, when the accessopenings are open, can be made without using a tool, whereby thereplacement of the first and second packings can be made more easily andquickly than in the conventional device.

INDUSTRIAL APPLICABILITY

As is apparent from the foregoing explanation, the present inventionrelates to a filter device for compressed air which has filter meanshaving suitable packings accommodated in respective sleeves, andadvantageously provides such a filter device wherein the suitablepackings can be easily and quickly replaced.

What is claimed is:
 1. A filter device for compressed air, includingfirst filter means having a first packing accommodated in a first sleevethereof, second filter means having a second packing accommodated in asecond sleeve thereof, an inlet passage portion defining an inletpassage which connects an exterior of said filter device and said firstsleeve to introduce said compressed air from said exterior into saidfirst filter means, a guide passage portion defining a guide passagewhich connects said first sleeve and said second sleeve to guide saidcompressed air from said first filter means into said second filtermeans, and an outlet passage portion defining an outlet passage whichconnects said second sleeve and said exterior to feed said compressedair out of said second filter means to said exterior, said compressedair which has been introduced through said inlet passage portion beingintroduced through said first filter means into said guide passageportion, whereby vapor or liquid particles contained in said compressedair are condensed or coalesced to be separated from said compressed air,said compressed air from which said vapor or liquid particles have beenseparated being further introduced through said guide passage portioninto said second filter means, whereby said liquid particles remainingin said compressed air are removed, said filter device beingcharacterized in that:said first and second sleeves, said inlet passageportion, said guide passage portion and said outlet passage portion areformed of a synthetic resin, integrally with each other, so as toconstitute a body of said filter device, said body being provided withaccess openings through which said first and second packings are removedfrom said filter device, each of said access openings being providedwith a closure member which is removably attached to each of said accessopenings so as to fluid-tightly close said access openings; said firstsleeve includes a communication portion which communicates with saidinlet passage portion and which is large enough to permit said firstpacking accommodated in said first sleeve to be removed therethrough,while said second sleeve includes a communication portion whichcommunicates with said outlet passage portion and which is large enoughto permit said second packing accommodated in said second sleeve to beremoved therethrough, said access openings being formed in said inletand outlet passage portions so that said first and second packings canbe removed through said access openings from said first and secondsleeves, respectively; and each one of said first and second packingscooperates with two retainer plates and a core bar to constitute acorresponding one of first and second filter elements, said two retainerplates each having a plurality of through-holes formed therethroughbeing disposed on axially opposite ends of said corresponding one ofsaid first and second packings, said core bar extending in an axialdirection of said corresponding one of said first and second packings topass a center of said corresponding one of said first and secondpackings such that said two retainer plates engage said core bar atrespective opposite ends of said core bar, said core bar being providedwith a pull tab at one of said opposite ends of said core bar, so thatsaid first and second packings are introduced into and removed from saidfirst and second sleeves, respectively.
 2. A filter device forcompressed air according to claim 1, wherein said first packing of saidfirst filter means is a metallic fiber aggregation which is formed byaggregating a large number of short or long fibers made of a metallicmaterial, and wherein said first filter element is formed by fixedlywinding said metallic fiber aggregation on said core bar.
 3. A filterdevice for compressed air according to claim 1, wherein said secondpacking of said second filter means is a belt-like fabric mesh formed ofcotton fibers, and wherein said second filter element is formed byfixedly winding said belt-like fabric mesh on said core bar.
 4. A filterdevice for compressed air according to claim 1, wherein said body isformed of a transparent synthetic resin, as a single unit.
 5. A filterdevice for compressed air according to claim 1, wherein said closuremember has at least one leg provided at a portion thereof opposed tosaid retainer plates and extending towards said retainer plates, andsaid closure member is attached to each of said access openings suchthat said retainer plates are pressed by said at least one leg of saidclosure member, whereby said retainer plates are prevented from movingtowards said access openings in said axial direction.
 6. A filter devicefor compressed air according to claim 1, wherein said pull tab includesa ring which is attached to one of said opposite ends of said core barsuch that said ring passes through a through-hole formed through saidcore bar at said one of said opposite ends, and wherein said ringprevents said retainer plates from moving relative to said core barwhich passes through center holes of said retainer plates.
 7. A filterdevice for compressed air according to claim 1, wherein said core barincludes a U-shaped portion which is elastically deformable, at theother of said opposite ends remote from said pull tab, said U-shapedportion having an engaging portion formed on outer side face thereof andpassing through a center hole of one of said retainer plates such thatsaid engaging portion engages a peripheral portion of said center hole,whereby said retainer plates are prevented from moving relative to saidcore bar.